Add tests for json-customize example

[fp024]

Summary

Adds JUnit tests for the json-customize example.

Motivation

This PR adds a reproducible JUnit test case to the struts-examples repository to make it easier to verify the behavior of the custom JSON writer configuration.

With Struts 7.1.1, the custom JSON writer configured by the json-customize example is used as expected. However, after changing only the Struts version to 7.2.1, the configured custom JSON writer no longer appears to be selected, and org.apache.struts2.json.StrutsJSONWriter is used instead.

The behavior can be reproduced or verified by changing only the Struts version to 7.2.1 and running the added tests.

Since the Struts main repository does not have the Issues tab enabled, I am submitting this to struts-examples as a reproducible test case.

Notes

The tests use "json-unit-assertj" to validate the serialized JSON output. The lastLogin field is validated by date format instead of comparing against a fixed value.

Thanks 👍

[lukaszlenart]

@fp024 you must rebase onto main branch

[fp024]

@lukaszlenart
Rebased onto the latest main branch. Thank you.

[fp024]

When flexjson excludes fields with null values, it leaves trailing keys behind, which results in an invalid JSON string. I have pushed an additional commit to resolve this issue.

[lukaszlenart]

Test ProduceActionTest fails

[fp024]

I added and shared this test case specifically because it fails on Struts 7.2.1 while passing completely on Struts 7.1.1.

On Struts 7.2.1, the following configuration does not take effect, and the system is seemingly forced to use only the default StrutsJSONWriter instead of our custom bean:

  <bean type="org.apache.struts2.json.JSONWriter" name="flexJSONWriter" class="org.demo.FlexJSONWriter"
        scope="prototype"/>
  <constant name="struts.json.writer" value="flexJSONWriter"/>

[lukaszlenart]

Thanks for that, I will double check what's wrong

[lukaszlenart]

Nice, this is regression in Struts 7.2.1, I will prepare a fix.

[lukaszlenart]

Ticket ready, on it
https://issues.apache.org/jira/browse/WW-5641

[fp024]

Thank you very much for checking. Have a nice day! 👍